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Based on my experience, you may encounter different roles according to the company role in the market, so based on the topics you may like, be sure to choose a company where you can develop and put in practice those skills, not only because they currently use them, but also when you foresee the potential of improving their operations with certain technology or toolbox.
Here are some that come to my mind:
DB admin - Call it SQL or NoSQL, but the Databases are the main concentration point of the stored data, which must be designed thinking on the applications which will consume them, so as a DB admin you must interact constantly with the end user of your data to design and improve the data access operations, working algo very close to the infrastructure engineer.
Operations/Infrastructure engineer - In charge of running the servers, configuring and granting the credentials needed to access a certain subnet of servers and
Automation engineer - Using scripts languages like bash or python, or tools with a higher level of abstraction, the main goal is to make common manual tasks faster and less error prone.
Tester - A testing engineer may sound boring in a first sight, but there are lots of automation tools and good practice methodologies that you may implement in a software lifecycle which may help in a massive way in the continuous and correct delivery of quality software to the client.
Back-end Engineer - Use the programming architecture that better fits or dictated by the architect, but use a lot of logic thinking in order to design and implement the procedures to treat the data and deliver it to the Front-end (If existent) in a clear and simple way, the better is the back-en developed, the faster and clearer will be the interactions between the different software pieces.
Front-end Developer - Your main goal is the user experience, provide not only beautiful and visually rich environments, but also simple and intuitive ones when needed, requires a lot of detail thinking and putting in the side of the end-user.
As you correctly mentioned, there may be many more roles (and many more with the new trends like Big Data and SDN), and most of time your daily work may require the use of multiple of them according to the company size or marked impact.
PD: Remember as well that following certain version control system and documenting is something that EVERYONE should do.
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